Due, in part, to the lack of standardized testing methods, relatively little data is available regarding olfaction in children. To remedy this situation, we have developed a pediatric olfactory test which makes use of five odorants found in the home which have been microencapsulated. The children identify the smell by pointing to one of five photographs depicting the test substances. Five blocks of the five test odorants are presented in random order within each block. The responses are quantified using confusion matrix analysis, which permits the determination of the percent correct identifications and the evaluation of the pattern of incorrect responses. We have established the normal range of responses for ages 4 to 10 years. Percent correct increases as a function of age, suggesting that olfactory maturation is not complete at birth and that development continues through childhood. If so, intrauterine events, environmental stimuli, or biological processes may alter or arrest olfactory development. For example, we found that some children, particularly boys, with midline structural defects (cleft lip and palate), are at increased risk for olfactory deficits. To determine if interruption of normal gestational events results in altered olfactory maturation, we plan to study olfaction in children born prematurely. Such children have an increased incidence of neurological deficits, but olfaction has not been specifically investigated. Since, in the neonatal period, small premature infants often experience olfactory deprivation from prolonged periods of assisted ventilation, it seems reasonable that this latter group might be particularly susceptible to olfactory deficits. We will test graduates of our intensive care nursery, now ages 4 through 13 years, with our pediatric olfactory test. Since animal studies indicate that hormones, particularly sex steroids, may modulate olfactory maturation, we will then study children with premature and delayed puberty. Lastly, to attempt to demonstrate that the improvement in olfactory scores with age is due to olfactory maturation rather than changes in cognitive function, test-taking abilities, or increased familiarity with odorants, we will utilize an olfactory learning task similar to the method employed in our pediatric olfactory test. The results of our study should permit us to begin to understand the olfactory maturation process, assist in identifying children at risk for olfactory deficits, and eventually devise treatment modalities for olfactory impairments.